An emerging concept of biomolecular dynamics and function: applications of NMR & MRI.

A new concept of protein dynamics has emerged quite recently, and a crucial link between protein dynamics and function has been largely established using recent NMR techniques in the solution state. Protein structure is governed by the thermodynamic principle and may not necessarily be unique in the solution state. Enzyme catalysis, protein folding or allosteric transition occurs on the microsecond to millisecond time scale, implying that in order to prepare the specific nuclear coordinate for the electronic state transition, a protein must rearrange its nuclear coordinates substantially, and this process may generally take a long period of time almost comparable to that of protein folding. Protein coordinates optimized for the electronic reaction may form an energy state--which may be called an "excited state"--that is thermodynamically distinct from the native state. In contrast, the native state is called a "ground state." Relevant NMR techniques developed recently may also have useful application to MRI, since the critical time scale of various reactions in a living system is also around micro- to milliseconds.